The invention relates to a new support and restraining device for arthrographic examination of the knees.
Arthrographic examination of the knees is a well known radiologic procedure for diagnosing lesions of the menisci which lie between the articulating surfaces of the knee joint. A complete description of the history of the technique, the anatomy of the knee joints and common arthrographic procedures and collateral leg supporting devices appear in a paper by Donald R. Westall entitled "Arthrography: A Critical Study of the Technique and Possible Improvement of Knee Arthrograms," Radiologic Technology, Vol. 45, No. 5, p. 311-321, 1974. Other monographs describing arthrography of the knee are by Freiberger et al, "Arthrography of the Knee by Double Contrast Method," Amer. J. Roentgenol, Vol. 97: 736-747, July, 1966; and by Andren et al, "Double-Contrast Arthrography of Knee with Horizontal Roentgen Ray Beam," Acta Orthro. Scandinav. 29: 307-314, 1960. All the material contained in the above articles is incorporated herein by reference thereto.
For convenience, a short description of the known arthrographic procedures are described hereinbelow.
All arthrographic procedures involve the injection of a contrast medium into the joint space surrounding the knee joint. The contrast medium envelopes and coats the menisci of the knee joint, thereby allowing the outline thereof to be visible on radiographs. By this means pathology of the menisci, and especially tears, can be detected.
There are three basic techniques for producing the radiographs for an arthrographic examination. These are: (1) the vertical ray technique (2) the fluoroscopic technique, and (3) the horizontal ray technique. The vertical ray technique utilizes a downwardly projecting X-ray beam through the knee joint. For reasons unimportant to this disclosure, this technique has not been widely utilized since the development of the fluoroscopic technique. The Fluoroscopic technique allows the radiologist to view the knee joint continually as it is rotated, thereby allowing him to evaluate both menisci in different projections. The main disadvantage of fluoroscopy is that the patient, radiologist, and the technologist are exposed to a great deal of unnecessary radiation. The best method for making an arthrographic study of the knee is by utilization of the horizontal ray technique. As the name implies, a standard X-ray machine is used to produce a horizontal X-ray beam which is made to pass through the patient's knee and onto a standard radiographic film cassette. Up to the present time, as shown in the article by Andren et al, supra, this has been performed by placing a small pillow under the patient's knee joint and a sandbag upon the ankle. This procedure flexes the knee joint and allows clear radiographs of the knee menisci to be obtained. While this is a reasonably good method of obtaining an arthrographic study of the knee joint, it is difficult, if not impossible, to accurately localize a lesion which has been discovered on a radiograph. This is due to the inability of the radiologist to determine the exact position of the knee during each radiographic exposure. Further, since the leg is not restrained, and the rotation of the knee about the femoral axis is not recorded, a particular projection cannot be accurately duplicated for more precise study. Also, the so-called sand bag technique shown by Andren et al, supra, does not insure that the patient's leg is held in the correct orientation with respect to the film holder and therefore the accuracy of the radiograph must always be, to some degree, suspect. Further, since the leg is not fully restrained from movement, the possibility of a blurred radiograph is always present.
The present invention relates to a support and restraining device which greatly improves the accuracy and reproducibility of radiographs produced using the horizontal Roentgen ray technique of knee arthrography. The device includes: a main horizontal base or platform which supports a novel leg clamping unit, a unique film holder, and a device for precisely indicating the degree of rotation of the patient's leg, the latter of which will be referred to herein as an arthrographic protractor.
The clamp unit includes a vertically adjustable horizontal support member which is adapted to support the weight of the patient's leg above the platform and an adjustable restraining device which quickly and easily secures the leg in a selective position on the support member. The restraining device secures the lower femoral section of the leg above the platform to permit the free end of the leg to cantilever downwardly under the force of gravity to thereby stress the knee in order to open the knee joint. This stressing or opening of the knee joint is necessary to produce clear, diagnostic radiographs. The clamp unit is situated on the platform with respect to the film holder so that the femur can always be restrained in a line parallel to the plane of the film holder. This construction again helps to provide accurate, reproducible radiographs of the knee.
The film holder includes a film elevator which adjusts the vertical level of the film in a facile manner in order to place an unexposed film frame directly behind the area of the knee to be examined. The film holder is also provided with an X-ray beam restricting frame for automatically producing a series of the most advantageously sized radiographs of the knee on a single film cassette. Also, the film holder is provided with film markers which, with a touch of the finger, will indicate on the radiograph whether the image is of the left or right leg and whether the meniscus being radiographed is the medial or lateral.
The support and restraining device is uniquely designed so that the clamp unit and the arthrographic protractor can be adjustably located on the platform to permit the examination of either leg of the patient without unnecessary discomfort to the patient.
The underside of the platform is provided with suction cups so that the device may be placed directly upon an X-ray table in a stable manner. Also, in keeping with the versatility of the device, a support for the main base, or understructure, is provided, also with suction cups therebelow. The understructure includes top and bottom horizontal members which are held apart by an upstanding wall member secured to parallel edges of the top and bottom horizontal members, which edges lie in the same vertical plane, and the distance between the top and bottom members is sufficient to permit the other leg of an adult patient to be rested therebetween. This feature not only aids in precisely positioning the knee to be studied with maximum patient comfort, but also allows the patient to continually roll his body as the leg supported in the device is incrementally turned when a series of radiographs are taken about one side of the knee, for example, the medial side of the right leg. A target film distance (TFD) indicator is also incorporated on the platform in order to aid the technician in quickly measuring the distance between the X-ray tube and the film.
It is therefore one of the main objects of the invention to provide a clamp unit which can be used quickly to position and secure a patient's knee in front of a film holder and which can easily release the leg for repositioning and subsequent resecurement.
It is another main object of the invention to provide a clamp unit which is vertically adjustable above a platform and which will support and restrain the lower femoral section of a patient's leg, be it an adult or a child, and which will thereby permit stress to be applied to the knee in order to open the joint for arthrographic study.
A further main object of the invention is to provide a radiographic film holder which is vertically adjustable, is provided with means to mark which leg and which side thereof is shown in the radiograph, and which automatically restricts the size of a single radiograph exposed on the radiographic film.
It is another main object of the invention to provide a support and restraining device for arthrographic examination of either the right or the left knee and either the lateral or medial side thereof with maximum patient comfort, while minimizing the amount of unnecessary radiation to which the patient is exposed.
It is still another main object of the invention to provide an uncomplicated, compact, and adjustable assembly which allows arthrogram radiographs to be obtained which are clearer, more accurate, and if necessary, precisely reproducible.
These, as well as other objects and advantages of the invention will become more apparent upon a reading of the following detailed description of a preferred embodiment, in conjunction with the drawings, wherein: